Shao Jian Ma

Direct Microwave Roasting of Arsenic-Bearing Pyrite Concentrates

Abstract Arsenic-bearing pyrite was used as an indicator to investigate microwave roasting behavior of pyrite concentrates. Appearance of the microwave roasted sample showed that the irradiation-induced transformation started from a small area of the crucible and gradually advanced to the remainder zone. X-ray diffraction (XRD) analysis showed that the arsenic contained in the pyrite was oxidized to As2O3, and that the pyrite was converted into pyrrhotite, hematite, and Fe3O4. The effect of the microwave power, the sample mass, and the microwave irradiation time on the roasting properties was also studied. The results showed that the mass loss ratio increased with the microwave power and the microwave roasting time.

Alkaline Leaching of Low Grade Complex Zinc Oxide Ore

Alkaline leaching is an important way for treating low grade metal oxide ore, which has some advantages such as low corrosion and low pollution compared to acidic leaching. In order to recover the zinc from a low grade complex zinc oxide ore in which the grade of Zn and Fe are 13 wt.% and 40.2 wt.%, respectively, and 52.8% of Zn is contained in siderite, 34.63% in limonite and 11.55% in smithsonite, this paper presents a preliminary investigation of this type of ore by alkaline leaching method. In this study, ammonia-ammonium chloride and ammonia-ammonium carbonate were used as the leaching reagents. The effects of alkaline concentration, leaching time, leaching temperature and liquid to solid ratio (L/S) were studied, respectively. The results show that 43.15% of initial Zn content was extracted adopting ammonia-ammonium chloride as the leaching reagent in 4.5M at 30°C for 3h with a liquid to solid ratio of 4:1, while 43.07% of Zn recovery was achieved employing ammonia-ammonium carbonate as the leaching reagent at 5M, 30°C and 4:1(L/S). The low leaching rate of Zn is probably attributed to that the zinc contained in siderite was not extracted completely because Zn and Fe exist as isomorphism in siderite.

Comparison of the Microwave Absorption Characteristics of Hematite, Magnetite and Pyrite

Abstract We provide an understanding of the microwave absorption characteristics of hematite, magnetite and pyrite by measuring and comparing the microwave heating rate, dielectric and magnetic properties and the absorbed microwave energy. The three methods have their own advantages and disadvantages, and supplement each other. Magnetite showed the strongest microwave absorption and rapid heating rate because of its dielectric and magnetic losses. Dielectric properties and calorimetry indicate that two pyrite samples had different microwave absorption characteristics, but a similar heating rate. Three types of hematite had a significant difference in interaction with the microwave. The heating rate of one of the hematite samples was most rapid and the sample had a higher dielectric loss factor. The ability of these minerals to absorb microwaves was maintained at a certain level when the microwave power and microwave heating time increased. For microwave-sensitive materials, the amount of absorbed microwave energy increased significantly with their mass.

Microwave Roasting Pyrite for Removal of the Sulfur and Arsenic

The application of microwave technique in the roasting pyrite which contained little arsenic was described. The characteristics of microwave absorption of pyrite were investigated. The results indicated that pyrite was a good absorbent of microwave and heated rapidly to high temperature by microwave flied in a short time, causing decomposition and oxidization to removal the sulfur and arsenic. The effects of microwave irradiation time and sample mass on the removal efficiencies of sulfur and arsenic with microwave power of 4 kW and 6 kW were investigated. The big microwave power could shorten the time for removal of sulfur and arsenic. Finally iron concentrate contained 64.52% Fe, S<0.1%, As<0.094% were obtained.

Hydrometallurgical Treatment of Low Grade Zinc Oxide Ore

In this research, a leaching study was carried out to assess the effect of several parameters on zinc extraction in a low grade complex zinc oxide ore in which the grade of Zn is 13 wt.%, and 52.8% of Zn is contained in siderite, 34.63% in limonite and 11.55% in smithsonite. The influencing parameters investigated include sulfuric acid concentration, reaction temperature, reaction time and liquid to solid ratio (L/S). The results show that over 90% of Zn can be extracted from the low grade complex zinc oxide ore when the leaching process is operated in 2M sulfuric acid at 60°C for 2.5h with a liquid to solid ratio of 6:1.

Sulfuric Acid Leaching on Low Grade Oxide Ore

In this paper, sulfuric acid leaching was carried out to assess the effect of several parameters on metal extraction in a low grade complex gossan ore in which the grade of zinc and iron is 13% and 40.2%, respectively. Parameters, such as sulfuric acid concentration, liquid to solid ratio and leaching temperature, were studied. The results show that the zinc leaching rate is almost 80%, while the iron leaching rate is about 45% used strong acid with 200g/L. It can be seen from the results that sulfuric acid leaching could not effectively recover zinc from gossan ores studied in this paper because of iron dissolving greatly.

The Preliminary Investigation of Low Grade Zinc Oxide Ore

Flotation is a conventional way for treating low grade metal oxide ore which has some advantages such as high efficiency and low cost. In order to recover the zinc from a low grade complex zinc oxide ore in which the grade of Zn is 13 wt.%, this paper presents a preliminary investigation of this type of ore by flotation method. In the experiments, the effects of different parameters such as grinding fineness, amount of Na2SiO3, amount of Na2S and amount of octadecylamine were investigated in relation to the metal contents of concentrates. The results show that about 35% of initial Zn content was obtained with 70% -200 mesh grinding fineness, 1000g/t Na2SiO3, 2000g/t Na2S and 500g/t octadecylamine. It is clear that the preliminary flotation tests with the ore sample indicated that there was no selectivity in terms of zinc recovery. Almost 65% zinc remained in the tailings and could not be recovered by flotation due to its complicated mineralogical structure. Therefore, application of metallurgical processes is proposed for zinc recovery from the tailings in the following investigations.

Study on Porous Structure and Surface Characteristics of Al-Pillared Montmorillonite

Al-pillared montmorillonite (Al-PILM) prepared with Keggin ions was studied by means of XRD, SEM-EDS and N2 adsorption-desorption isotherms.The rusults show that, compared to unpillared Na-montmorillonite (Na-M), the interlayer spacing d(001) value, BET specific surface area, surface fractal dimension and the proportion of microporous specific surface area of Al-PILM are larger and the surface is relatively rough. The BJH porous volume distribution of Al-PILM is the most probable distribution, and the most probable pore size is about 2 nm, belonging to mesopore. The porous structure of Al-PILM is characterized as parallel plate slit or “house-of-cards” wedge-shaped pore which is formed by novel meso-microporous delaminated structure and fragments. Besides, the results of elemental distribution show that the ions exchange action between Na+ and hydroxy-Al cations in pillaring solution occurs in the formation of Al-PILM.

Experimental Study on Microwave Pretreatment with some Refractory Flotation Gold Concentrate

The microwave pretreatment of a typically refractory flotation gold concentrate was investigated. The results demonstrated that a maximum gold recovery of 97% was achieved, and that gold recoveries of the refractory gold concentrate quickly increased to the maximum with microwave heating time. Adding additives during microwave heating process was helpful to improve the leaching rate of gold, and the effect of microwave heating with single NaOH on the leaching rate of gold is not better than that of NaOH combined with other additives.

Study on Microstructure Variation Laws of Al-Pillared Montmorillonite

Al3+/clay ratio is one of the important factors influencing microstructure of Al-pillared montmorillonite. Microstructure variation laws of Al-pillared montmorillonite prepared under the condition of different Al3+/clay ratio are systematically studied by XRD, FTIR, specific surface area and pore size analysis. The results show that the interlayer spacing and BET specific surface area of Al-pillared montmorillonite are remarkably affected by the Al3+/clay ratio. The interlayer spacing d(001) value and BET specific surface area of Al-pillared montmorillonite increase firstly and then decrease with the increases of the Al3+/clay ratio, and they reach to maximum when the Al3+/clay ratio is 10mmol/g. Besides, the BJH porous volume distribution of Al-pillared montmorillonite is the most probable distribution, and the most probable pore size is about 2 nm, which is attributed to mesopore. The porous structure of hydroxy-Al pillared montmorillonite is characterized as parallel plate slit or “house-of-cards” wedge-shaped pore which is formed by novel meso-microporous delaminated structure and fragments. With the increase of the Al3+/clay ratio, BJH total porous volume and mesoporous volume of hydroxy-Al pillared montmorillonite decreases, while the proportion of microporous volume in the total porous volume increases. The proportion of microporous specific surface area of all the hydroxy-Al pillared montmorillonite samples is about 62% and is much larger than that of Na-M and those of mesopore and macropore, indicating the main action of intercalation of hydroxy-Al pillaring solution into montmorillonite interlayer is to increase the micropore amount.